1. Field of the Invention
Embodiments of the invention relate to the field of semiconductor device fabrication. More particularly, the present invention relates to an apparatus and method for measuring the incidence angle for an ion beam in an ion implanter.
2. Discussion of Related Art
Ion implantation is a process used to dope impurity ions into a semiconductor substrate to obtain desired device characteristics. A precise doping profile in a semiconductor substrate and associated thin film structure is critical for proper device performance. An ion beam is directed from an ion source chamber toward a substrate. The depth of implantation into the substrate is based on the ion implant energy and the mass of the ions generated in the source chamber. In addition, the beam dose (the amount of ions implanted in the substrate) and the beam current (the uniformity of the ion beam) can be manipulated through the use of a mass analyzing magnet, a corrector magnet and one or more acceleration and deceleration stages along the ion beam path to provide a desired doping profile in the substrate. However, throughput or manufacturing of semiconductor devices is highly dependent on the uniformity of the ion beam on the target substrate to produce the desired device characteristics.
Generally, beam current, energy contamination and uniformity both of ion beam current density and angle of implantation are the parameters that jeopardize device throughput during semiconductor manufacturing processes. For example, if the beam current is too low, this will reduce the throughput of the implanter for a given total ion dose. Energy contamination occurs when there is a small fraction of the ion beam that is at a higher energy than desired. This small fraction of the ion beam at a higher energy level will rapidly increase the depth of the desired junction that is formed in the substrate when creating an integrated circuit and lead to degraded performance of the desired circuit profile. If the ion beam current density and angle of implantation are not uniform, there will be variations in the device properties formed across the semiconductor substrate. These variations in beam current and angle of implantation can compromise the desired device characteristics which could produce lower manufacturing yields and lead to higher processing costs. Thus, there is a need to control at least one or more of these parameters to provide current uniformity for ion implantation systems when manufacturing semiconductor devices.